Glass fibers are typically produced by drawing molten glass at a high rate of speed from tips of small orifices in a precious metal device or bushing. During the forming and subsequent mechanical and treatment processes, the glass fibers can be broken by contact with each other and processing equipment (i.e., a process known as filamentization). These broken glass fibers (fuzz) can accumulate on processing equipment and/or produce an undesirable non-uniform surface on polymeric articles to which the glass fibers are added.
To protect the glass fibers from interfilament abrasion, a sizing composition is applied to the surface of the glass fibers during the forming process. Typical sizing compositions include components such as film-formers, lubricants, coupling agents and emulsifiers. Generally, the sizing composition is applied to a glass fiber strand subsequent to the drawing process and prior to gathering of a plurality of continuous strands on a forming package. The forming packages are typically dried to remove moisture and cure the sizing composition.
Glass fibers can be incorporated into polymeric materials by filament winding, pultrusion, and other processes for forming high strength glass fiber reinforced molding composites. Pultruded profiles are commonly used in corrosion resistant applications in which corrosion resistance, electrical resistance and high strength are desired. Examples of pultruded products include architectural and automotive products, ladder rails, sucker rods, antennas, railings, conduits, I-beams, H-beams, angles, insulator rods, floor gratings and roadway delineators.
The strength of molded products formed from materials produced by the above processes is dependent in part upon the degree of contact between the polymer and fiber glass. The measure of the flowability of the polymeric matrix material through the glass fiber mass to obtain essentially complete encapsulation of the entire surface of each glass strand by the polymeric material is referred to as "wet-out". Incomplete wet-out during this initial processing can adversely affect subsequent processing as well as the surface characteristics of the final composite. For example, poor wet-out can manifest itself as low composite strengths and the fibers can appear white in the composite.
It is desirable to have optimum wet-out and compatibility of the glass fibers with the thermosetting matrix resin in applications such as those discussed above.